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Power to heated bed M2

Posted: Sat Dec 12, 2020 4:30 pm
by sonra
Saturday nice day so I turn on my M2 printer . Heated bed temp=0 . Check wires OK . Check PS output 3 output =24v . Check on the Arduino TB
no power on HBP connector .Try Power UP again the some result . Heater and Fan board connectors got 24v .try to check 3 fuses they are fine .
Try to unplug the HBP from connector and check directly or the board connector but the some result . Any idea ( problem in Arudino board ?)
Regards Doron

Re: Power to heated bed M2

Posted: Sat Dec 12, 2020 6:10 pm
by jferguson
My M2E board quit heating, but thermistor still worked.

I found that the HB 24v positive pin in the connector on my plug was badly corroded. Obviously there was power at the plug which could be measured by touching DMM probes to the screw heads atop the connector, but there was no connection at the pin itself to the board.

If this is your problem, you may be able to see it in the connector.

For a while it was intermittent, sometimes worked sometime didn't.
I replaced the plug. Mouser sells Wurth plugs and jacks which although not Molex will work just fine and have slightly higher amp ratings. They are green rather than black. If your jack is a mess, you can desolder it and replace it with the Wurth equivalent. Although I was able to find replacement Molex plugs, no-one in the US stocks the jacks.

You can see where the hot + connection burned through the body of the connector. I have no real idea what the problem was. Nothing wrong with the heat bed, and the board with the replaced connector works fine. The jack shows some rust-like stuff where this pin is. The pin itself looked "rusted" but of course it isn't ferrous so ???

This system can run its print and then be left on for a few days until i can get back to the shop. It could be that the mosfet imposes some load on the + 24v HB line even when there is no printing and ultimately the connector heats up and this happens.

I will continue to have to leave my printer alone for days after a print is completed. My solution is to install a TP Switch in line with the M2 power supply and turn it off at the end of a print/

Re: Power to heated bed M2

Posted: Sat Dec 12, 2020 11:53 pm
by sonra
When it disconnect the 2 pin TB from the board and check directly on the pins of Arduino board I don't have 24v so I have a different problem
Thanks for try to help

Re: Power to heated bed M2 (problem solved )

Posted: Mon Dec 14, 2020 2:58 pm
by sonra
the problem was the HBP thermistor .(good i have other one ) i suppose that when the MF feels problem in the thermistor it does not turn on the power to the HBP